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Monday, 11 February 2013

2012 DA14 radar parameters

EISCAT pointings for the asteroid pass. Based on the energy to noise ratio, we estimate that we can observe until 01:00 UT before losing signal. The vertical lines indicate when the different radars start observing (solid=EISCAT, long dashes=Haystack, short dashes=Goldstone).

Right now I'm doing some programming to allow EISCAT to track the asteroid during the pass. This will involve translating NASA Horizons ephemeris tables into pointing commands that are given to the radar -- possibly involving offsets. With recent observations, the errors are getting smaller and smaller, which increases the chances of hitting the target. Luckily our radar is so small, that the 0.1 degree 3-sigma errors are already much less than the 0.5 degree antenna beam width.

As you can see from the figure above, the asteroid will appear from the East and then head approximately towards zenith. The target will be fast, but not even close to the limits of the tracking speed of the radar. I've estimated the radar cross-section by assuming it is 0.1 times that of a metallic sphere with a diameter of 50 meters. I've estimated the energy to noise ratio based on a 0.1 second coherent integration time and a 12.5% duty-cycle (the maximum that EISCAT can do).

As for coding, I intend to use 200 different codes with a 10 us baud length and the EISCAT maximum 2 ms pulse length. This is to allow a real-time analysis, but still leaving quite many phase transitions for high resolution analysis. I'll be sampling at 10 MHz, which covers the 7 MHz receiver bandwidth at EISCAT.